Influences of the Three Gorges Project on seismic activities in the reservoir area

Reservoir-induced earthquakes related with the construction of the Three Gorges Project have attracted great concerns of the public. Since the first water impoundment on May 25, 2003, a number of earthquakes have occurred during the water storage stages, in which the largest was the Badong M5.1 earthquake on December 16, 2013. In this paper, the relationships between seismic activities, b value, seismic parameters, and reservoir water level fluctuations are studied. In addition, based on the digital seismic waveform data obtained since 2000, the focal depth changes and focal mechanism characteristics before and after the water impoundment are studied as well. These provide us important information to understand the earthquake mechanisms. The results show that these earthquakes are typical reservoir-induced earthquakes, which are closely related to water infiltration, pore pressure, and water level fluctuations.The majority of the micro and small earthquakes are caused by karst collapse, mine collapse, bank reformation, superficial unloading, and so on. The larger earthquakes are related to the fault structures to some extent. Due to the persistent effects of water impoundment on the seismic and geological environments around the reservoir and water infiltration into the rocks, the influences on the crustal deformation field, gravity field, seepage field, and fault medium-softening action may vary gradually from a higher strength to a weaker one. Therefore, it is possible that small earthquakes and few medium earthquakes(M≤5.5) will occur in the reservoir area in the future.

Effect of seed particles content on texture formation of Si_3N_4 ceramics by gel-casting in a strong magnetic field

In this paper, the textured Si3N4 ceramics were prepared by adding seed particles during gel-casting in the magnetic field of 6 T, followed by pressureless sintering. The effect of pH on the stability and dispersibility of Si3N4 slurry and the effect of seed particles content on texture formation of SiaN4 ceramics were both studied. Those results showed that the slurry with good stability and dispersibility was obtained when pH was about 11.6. The a or b-axis of Si3N4 particles or crystals was aligned parallel to the direction of the magnetic field in the magnetic field of 6 T. The degree of texture of Si3N4 ceramics further increased during sintering. With the increasing of additional β-Si3N4 particles in the magnetic field of 6 T, the degree of texture increased from 0.19 without seed particles to 0.76 with 9% （mass fraction） seed particles. The increase of seed particles content promoted the texture formation of Si3N4 ceramics.

Microstructure and properties of MOCVD-derived Gd_xY_(1-x)Ba_2Cu_3O_(7-δ) films with composition fluctuations

The effects of Gd content on crystalline orientation, microstructure and superconductivity of GdxYl-x-BazCu3O7-δ（GdYBCO） films were systematically investigated. By varying the Gd content in the liquid precursor without changing the total amount of rare earth elements, series of GdYBCO films with x values of 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0 were fabricated by metal organic chemical vapor deposition （MOCVD）. X-ray diffraction （XRD） and scanning electron microscope （SEM） analysis revealed that Gd introducing could restrain the formation of CuYOa phase, but induce a-axis growth of GdYBCO film. The increase of x from 0 to 0.5 leads to enhancing critical current density at self-field and 77 K （Jcs0 from 1.8 to 2.8 MA.cm^-2, which benefits from the decrease in CuYO2 impurities and improvement of in-plane texture from 5.0° to 4.3°. However, raising x from 0.5 to 1.0 gives rise to abundant a-axis growth of film and degradation of in-plane texture from 4.3° to 5.4°, consequently resulting in the decrease OfJcsf from 2.8 to 0.8 MA.cm^-2. Even though Jcsf has not varied monotonically, the critical transition temperature of GdYBCO films linearly increases from 90.75 to 92.25 K and the in-field performance at magnetic field （B） of 0-1.1 T and 77 K as well as B parallel to film normal is also superior with Gd content increasing.